X-ray crystallography is currently the most favored method for structural determination of proteins and other macromolecules. The requisite for a successful X-ray crystallographic application is to obtain single crystals of the target protein. Data is then collected by diffracting X-ray from the single crystal that has an ordered pattern of atomic orientation. The assembly of atoms and molecules in the crystal can be deduced from the measurement of X-ray scattering.
At present, more than 120,000 protein structures resolved by X-Ray crystallography experiments have been deposited in protein databank, accounting for nearly 90% of the resolved proteins, suggesting a predominant popularity of X-Ray crystallography in structural determination.